Embodiments of the invention generally relate to a propeller system of a rotary wing aircraft, and more particularly, to a system for controlling the pitch of a variable pitch propeller system of a high-speed rotary wing aircraft.
A rotary wing aircraft with a rigid coaxial contra-rotating rotor system is capable of higher speeds compared to conventional singe rotor helicopters due in part to the balance of lift between the advancing sides of the main rotor blades on the upper and lower rotor systems. To still further increase airspeed, supplemental translational thrust is provided by a translational thrust system, such as a propeller system oriented substantially horizontal and parallel to the aircraft longitudinal axis to provide thrust for high speed flight. The thrust generated by the variable pitch propeller translational thrust system is affected by varying the pitch of the propeller blades individually as the rotor rotates and by varying the pitch of at least one of the plurality of propeller blades.
Prior art high speed, coaxial, rotary wing aircrafts utilize translational thrust provided by one or more turbojets. The collective control of such aircrafts commonly include at least one twist grip throttle to control the turbojets. An operator applies a rotational force to the twist grip in a first direction to increase fuel flow to the engine, resulting in increased thrust of the aircraft. If a rotational force is applied to the twist grip in a second, opposite direction, the fuel flow supplied to the engines is decreased, thereby reducing the thrust output of the engine.
Therefore, the introduction of a variable pitch propeller translational thrust systems necessitates the need for a new control and interface to allow the pilot to directly control propeller thrust output.